Experimental and Monte Carlo studies on the response of CR-39 detectors to Am-Be neutron spectrum

ABSTRACT

The Poly-Allyl Diglycol Carbonate [PADC] detector is of particular interest for development of a fast neutron dosimeter. Fast neutrons interact with the constituents of the CR-39 detector and produce H, C and 0 recoils, as well as [n, a] reaction. These neutron- induced charged particles contribute towards the response of CR-39 detectors. Material and Electrochemical etching was used to enlarge track diameter which was made by low energy recoil protons. Before electrochemical etching, a chemical etching was performed for 1 hour. The responses were also calculated by Monte Carlo simulations, using MCNPX code in different energy bins considering H, C and O recoils. The total registered efficiency and partial contributions of the efficiency, due to interactions with each constituent of CR-39, were calculated. The optimized condition of etchant was obtained to be 6N KOH 15kV.cm[1], and 6 hours etching time. The obtained results show that track efficiency of CR-39 was a function of incident neutron energy. The tracks caused by O and C recoil nuclei were negligible for neutron energies lower than 1 MeV. At neutron energies lower than 1 MeV, only recoil protons would have sufficient energy to leave visible tracks. But, O and C recoils had important contributions in overall response of PADC at neutron energies of few MeV. The efficiency of a CR-39 based dosemeter could be calculated by MCNPX code and the results were in a good agreement with experimental results in energy range of [241]Am - Be bare source and [241]Am-Be was softened with a spherical polyethylene moderator of radius of 20 cm